Premortem Agent Skill

Premortem

Premortem is an optional plan-challenge strategy. It asks one fresh context to

identify concrete ways the resolved bead or caller intent could fail before implementation.

It is not part of the required RPI sequence and does not authorize readiness.

Workflow

• Resolve the existing intent source and derive its digest; inspect acceptance,

non-goals, evidence requirements, and declared write scope there.

• Use one fresh judge with a context ID distinct from the plan author.
• Test acceptance completeness, edge behavior, scope, dependencies,

reversibility, and evidence shape against cited repository facts.

• Return one complete set of concrete findings and checked/not-checked scope.
• Stop. The caller decides whether to revise the plan or invoke RPI.

Council or Dueling Idea Genies may be caller-supplied evidence, but Premortem

does not require either strategy and cannot turn consensus into approval.

Adversarial defeat attempts

Actively try to construct each failure, not imagine it. For every candidate

failure, attempt a concrete defeat: write the input, command sequence, or

repository state that would make the plan fail, and run or cite the check

that shows whether the plan survives it. A finding is reportable as concrete

when it names the defeating construction and what the plan does when it

lands; a failure you could not construct is reported as attempted-and-blocked

with the obstacle named, which is itself evidence for the plan. The named

failure mode is armchair pessimism: a list of imagined risks with no

construction attempts, which reads as diligence while testing nothing. Stop

condition: every reported finding is backed by a defeat attempt — constructed,

or attempted with the blocking fact cited; a finding with neither is deleted,

not softened.

Derivation-diff challenge

A challenger that critiques the handed plan is a yes-man with extra steps: it

anchors on the author's design and rationalizes it. Derive independently, then

diff. Give one fresh context ONLY the intent source and the plan's declared

ground truth — the vendor docs and stock behavior for integration work, the

repo's patterns and behavior spec for extension — and never the author's design.

Have it sketch its own design from that ground truth alone. The diff between that

independent design and the working plan is the challenge artifact; each

divergence is a finding to defend or adopt. Convergence is weak evidence the plan

follows the ground truth; divergence names where it may not.

Two questions the challenger answers with an artifact, not an opinion:

• Cathedral: is this the smallest real thing, or does it rebuild what already

exists? Artifact — the simplest version that satisfies acceptance, plus the

named reason it is insufficient. No named reason means build the simple one.

• Grain: for integration work, does every component the plan writes have a native

counterpart in the substrate? Artifact — the native-counterpart list, one row

per component the plan authors, naming the substrate feature it duplicates or

the reason none exists.

These are integration- and extension-class checks. The Grain question's

native-counterpart list applies only to integration-class work; do not impose it

on routine feature work.

Boundary

• Emit advisory findings, no verdict of any version, readiness, admission, or permission.
• Do not implement, validate the candidate, retry, repair, schedule, claim,

change acceptance, operate Git, close work, release, or deliver.

• Any plan edit creates a new subject for a later caller-initiated Premortem.

Output

Return premortem-plan-review.v1 with the intent digest, author and judge context

IDs, findings, evidence references, checked, and not_checked. An empty

finding set means only that this optional challenge found no concrete defect;

it is never a lifecycle gate.